This program encompasses a broad laboratory and clinical research program aimed at clarifying the basic mechanisms involved in heart attack (acute myocardial infarction) and ischemia (inadequate coronary flood flow) in man and in experimental models with the goal of providing a better understanding of the natural history of myocardial infarction, of the effects of surgical and medical therapy in patients with coronary heart disease (angina pectoris, heart attack, dysrhythmias, and cardiac failure), and of new forms of therapy for these conditions. The experimental models employed include studies on ischemia in isolated tissues, acute experiments in a variety of animal preparations, studies on ischemia and infarction and their treatment in chronically instrumented, unanesthetized animals and subhuman primates. Both the clinical and laboratory research programs bring to bear such techniques as hemodynamic and radiographic analyses, radioisotopes, echocardiography and other noninvasive methods, ultrasonic devices, measurement of serum enzymes and isoenzymes, electronmicroscopy and basic biochemical measurements of energy use and tissue repair in heart muscle to bear on the solution of these problems.